How do you access the matched groups in a JavaScript regular expression ?

Try this code for accessing groups of javaScript regular expression :

var myString = "something format_abc";
var myRegexp = /(?:^|\s)format_(.*?)(?:\s|$)/g;
var match = myRegexp.exec(myString);
console.log(match[1]); // abc

There are multiple matches you can perform over them by this code:

var myString = "something format_abc";
var myRegexp = /(?:^|\s)format_(.*?)(?:\s|$)/g;
match = myRegexp.exec(myString);
while (match != null) {
  // matched text: match[0]
  // match start: match.index
  //  capturing group n: match[n]
  console.log(match[0])
  match = myRegexp.exec(myString);
}

In this method you can get the n​th capturing group for each match:

function getMatches(string, regex, index) {
  index || (index = 1); // default to the first capturing group
  var matches = [];
  var match;
  while (match = regex.exec(string)) {
    matches.push(match[index]);
  }
  return matches;
}
 
// Example :
var myString = 'something format_abc something format_def something format_ghi';
var myRegEx = /(?:^|\s)format_(.*?)(?:\s|$)/g;
 
// Get an array containing the first capturing group for every match
var matches = getMatches(myString, myRegEx, 1);
 
// Log results
document.write(matches.length + ' matches found: ' + JSON.stringify(matches))
console.log(matches);